Analyzer for third elements in a hydrocarbon sample

ABSTRACT

A laboratory type of analyzer for quantitatively determining the percent third element content of a hydrocarbon sample. A unique rhodium/americium radioactive source is disclosed.

United States Patent [191 Alessio et al.

[ ANALYZER FOR THIRD ELEMENTS IN A HYDROCARBON SAMPLE [7 5] Inventors: Robert M. Alessio, Westmoreland;

Myron N. Palmer; Thomas J. Puzniak, both of Allegheny, all of Pa.

[73] Assignee: Gulf Research & Development Company, Pittsburgh, Pa.

[22] Filed: Mar. 12, 1971 [21] Appl. No.: 123,524

52 US. Cl. .,.....250/363 51 Int. Cl. sou *1/16 58 Field of Search 250/435 D, 43.5 MR,

, SINGLE 1C HAN/VEL AA/AL VZER AMPLIFIER Nov. 20, 1973 [56] References Cited UNITED STATES PATENTS 3,602,71 1 8/1971 Arora et a]. 250/84 2,295,975 9/1942 Storm 250/105 Primary Examiner.lames W. Lawrence Assistant Examiner-Davis L. Willis AttorneyMeyer Neishloss, Deane E. Keith and William Kovensky [57 ABSTRACT A laboratory type of analyzer for quantitatively determining the percent third element content of a hydrocarbon sample. A unique rhodium/americium radioactive source is disclosed.

14 Claims, 8 Drawing Figures HIGH VOL 77166 MWER SUPPL V PATENIEDrmv 20 ms SCAL ER OUTPUT S/A/GLE CHANNEL A/VAL y zse SHEET 10F 5 /7/6-'H VOL 7:465 POWER SUPPL V PAIENTEUMJYZO 1915 3374.027 SHEET 30F 5 mum/rags. 205RT M. 41.555/0 MVROA/ N. PALMER 7/10/1445 J. PUZ/V/AK SHEET [if PATENIED NOV 20 I973 //\/|/EN70R$. 4055 M AL 555/0 MVQO/V M PALMER 77/0/1045 J. PUZ/V/AK Kev Fig. 6

ANALYZER FOR THIRD ELEMENTS IN A HYDROCARBON SAMPLE Broadly, this invention pertains to methods and apparatus to analyze a hydrocarbon material also containing some other element for the percent content of said other element. More specifically, this invention relates to the determination of the sulfur content of hydrocarbon fluids.

The invention will be described with regard to analyzing a hydrocarbon to determine the percent content of sulfur therein. However, as will appear more clearly as the description proceeds, the invention can be used to analyze for the percent content of any element in a hydrocarbon material so long as the mass attenuation coefficient of said third element is substantially different from the mass attenuation coefficient of hydrogen and carbgn atabp ut Key, lt willjherefore be understood that the use of the word sulfur herein shall not be construed as limiting the invention to sulfur analysis, but shall also include analysis for all such heavier elements which may be found in hydrocarbons, such as lead, nickel, iron, and vanadium.

In the refining of hydrocarbons, it is important to know, as precisely as possible, the percent sulfur content of many process streams for many different reasons. In some situations it is necessary to know the percent sulfur content because a certain minimum sulfur content is required. An example of this situation is where a catalyst must be used in the presence of a certain amount of sulfur in order to partake in the reaction. In other situations it is necessary to know the sulfur content for the opposite reason. No more than a certain maximum sulfur content is permissible, and if there is too much sulfur in the process stream it must be removed. Examples of this situation include, for example, the production of certain special lubricants such as refrigerator or transformer oils, wherein a product sulfur content above a certain level may cause the formation of sludges in the oils, and/or may disturb oxidation stability. Another example where excess sulfur is undesirable is where the catalyst will be poisoned by too high a sulfur content. Still another example of where sulfur content must be known in order to keep it below certain minimums is in the refining of certain oils wherein the sulfur content must be kept below certain minimum levels since, upon combustion, the sulfur will produce compounds which are undesirable in the atmosphere.

The invention provides means to accurately, rapidly and inexpensively determine the sulfur content of many different hydrocarbons by the use of a radioactive energy source in such a manner as to cause cancellation of the hydrogen and carbon contents in the hydrocarbon, whereby the apparatus of the invention is sensitive to only the percent sulfur content.

This invention should be distinguished from process type analyzers which are used on-stream, i.e., connected into a flow. The present invention is a laboratory instrument, i.e., stationary samples are handled. Each of these general types of instruments has its own advantages. A process or on-stream analyzer provides rapid and continuous output, but such a device is limited to operation with a single process. A laboratory instrument has the advantage of versatility, it can be used for many different streams in a refinery, but this versatility is obtained at a cost in speed since samples must be brought to the laboratory. Another advantage of a laboratory instrument is that the need to make density corrections is eliminated, as will appear in more detail below. Another advantage of laboratory instruments and also of the present invention over process type instruments is their lower cost. The laboratory instrument is simpler, no sample flow connections are required, and less sophisticated electronics are required. Another advantage of the invention is that less time is required for an analysis than a process type analyzer would need.

The apparatus of the invention utilizes a radioactive sp tum-2 .1 s u e t adi t qns f u i hbsm: bard a rhodium target to produce fluorescent X-rays having a relatively narrow energy spectrum peak with an average energy at about 20 Kev. Several advantages over prior known atomic sources flow from this particular combination of source and target. Americium-241 has a half-life of 458 years. This exceedingly long halflife obviates the need for the heretofore usual source decay corrections, obviates the need for frequent recalibration, and provides a substantially maintenance free apparatus.

A second important advantage is that a very narrow, i.e., sharp, energy distribution occurs at about 20 Kev with this particular combination of source and target. The sharp energy distribution is important to the method of the invention because the mass attenuation coefficients of hydrogen and carbon are virtually identical at about 20 Kev, thereby permitting the absorption effects of the hydrogen and carbon to be considered together, leaving the sulfur content solely responsible for variations in transmitted X-rays. As is known, the mass attenuation coefficient of a material is a number representative of the total probable ability of that material to reduce the intensity of the transmitted beam by compton scattering or photoelectric absorption. The manner of operation of the invention will appear more clearly in the detailed description below.

Prior known combinations of radioactive sources and targets do not produce a sharp energy distribution at 20 Kev, or do not have the advantage of the long half-life of the americium/rhodium combination of the invention, or lack both of these advantages. For example, the use of radioactive strontium and a uranium target produces X-rays having a maximum intensity at about Kev, with a low intensity tail to 2.2 Mev, thus rendering it unsuitable for use in the invention. Another prior known combination is a radioactive promethium 147 source and an aluminum target. This combination has a relatively short half-life of 2.6 years and, although it does have an energy peak near 20 Kev, the peak is quite broad with an average value of about 25 Kev. With the americium/rhodium combination of the invention, both the average value and the maximum value of density of secondary X-rays produced by the target falls almost exactly at 20 Kev.

The americium/rhodium source combination of the invention provides advantages over an americiumlmolybdenum source mentioned in the prior invention described in co-pending application Ser. No. 738,288, filed June 19, 1968, by S. K. Arora and D. F. Rhodes, entitled Method and Apparatus for Determining Sulfur Content in Hydrocarbon Streams, now issued as US. Pat. No. 3,602,711, and assigned to the same as signee as the present invention. The invention also provides advantages over an americium/silver source. As

mentioned above, at about 20 Kev the mass absorption coefficients of carbon and hydrogen are equal. As set forth in the above-mentioned patent, a moly/am source produces energy sufficiently close to 20 Kev that the effects of carbon and hydrogen effectively cancel. However, the energy of the moly/am source is further from the ideal point than is the energy of the source of the invention, and in a laboratory analyzer this difference is more significant because the carbon/hydrogen ratio in a process stream does not change as dramatically as it does when going from sample to sample. Therefore, in a lab instrument the source energy must be closer to the carbon/hydrogen cancellation energy than in a process analyzer.

Another advantage of the rhodium/americium source combination of the invention is that the amount of error in percent sulfur detected at varying carbon/hydrogen ratios is very small. That is, as we have experimentally shown, at different carbon/hydrogen ratios, such as for example 6 to l for cyclohexane versus 12 to l for benzene, different source and target arrangements will produce different errors in amount of sulfur detected. Our rh/am source produces virtually no error as a result of different carbon/hydrogen ratios, thereby eliminating a source of error which prior sources did not accommodate. The source of this error, briefly, is that at energies displaced from about 20 Kev carbon and hydrogen absorb differently. Thus, for materials with a high carbon/hydrogen ratio, a greater total energy is absorbed, and this larger energy translates into a false greater amount of sulfur in the sample.

The above and other advantages of the invention will be pointed out or will become evident in the following detailed description and claims, and in the accompanying drawing also forming a part of the disclosure, in which: FIG. 1 is a cross-sectional elevational view, partly diagrammatic, of an instrument embodying the invention; FIGS. 2 and 3 are cross-sectional views taken on lines II-II and III-III of FIG. 1 respectively; FIGS. 4 and 5 are cross-sectional views taken on lines IV-IV and V-V of FIG. 3 respectively; and FIGS. 6, 7 and 8 are curves illustrating experimental results illustrating some of the advantages of the rh/am source of the invention.

Referring now in detail to the drawing, reference numeral 10 generally indicates apparatus and electronics embodying the invention. Electrical energy is supplied from a supply 1-2 via a line 14 to the remaining apparatus. A train of pulses produced by the analysis is present on a line 16, the rate of which pulses is related to the sulfur content of the sample being analyzed. The height of each pulse is directly proportional to the energy of the X-ray which produced that pulse. The train of pulses are transmitted, via an amplifier 18, to a Single Channel Pulse Height Analyzer (S.C.A.) 20. Amplifier 18 serves to strengthen the pulse for further handling. S.C.A. 20 removes spurious portions of the signal, and limits the signal passed on to that portion thereof which is produced by energy transmitted through the sample cell, described below, at about 20 Kev. S.C.A. 20 may contain a pair of discriminators set to bracket the peak of each pulse at about 20 Kev. Thus, the signal in line 22 after the S.C.A. is similar to the signal in line 16 but modified by the exclusion of portions of the signal other than those portions pro duced by about 20 Kev energy. Viewed in another way, the S.C.A. can be thought of as a kind of filter to produce a signal in line 22 related only to the amount of sulfur in the sample. Timer 24 and scaler and output device 26 together serve as a kind of timed pulse counter to produce a signal indicative of sulfur content. The scaler 26 sums up the pulses received per unit time as determined by timer 24, and this results is proportional to sulfur content.

The array of components 18 to 24 is exemplative of one method of producing the desired result. The action of the S.C.A. 20 serves to sort out the different energies passed through the sample and to examine only the energy at about 20 Kev. As will be evident to those skilled in the art, other means in lieu of items 18 to 24 could be used, for example, an ionization gauge type scheme, with means to correct for the hydrocarbon background, which, of course, would also require an ionization gauge in lieu of certain other items in housing 134.

The remaining apparatus comprises a source section 28, a sample section 30, and a pulse generating section 32.

Source section 28 comprises a cylindrical tube member 34 having an inner end annular mounting flange 36, and formed with threads 38 at its upper free end. The flange 36 may be integral with the main tubular body 34 or may be fixed thereto by any suitable means, such as welding. A spacer member 40 is positioned against the flange 36 and closes off the inner end of the tubular body 34. As appears more clearly in FIG. 2, spacer 40 is formed with a central opening 42 and with a slot 44 disposed in the plane of spacer 40 and extending from the outer cylindrical edge thereof to surround opening 42. This slot 44 permits the insertion of a strip of aluminum or other suitable material to attenuate the flow of X-rays from the source to the sample, in the usual manner. This control is needed to obtain a reference absorption count with no sample in the radiation path. This reference absorption count is then used to relate subsequent sample absorption counts to the calibration curve for the analyzer. The slot also accepts a strip of lead which prevents X-rays from passing through the sample loading chamber when not in use.

The spacer 40 is preferably made of linen backed Ba kelite or other suitable strong insulating material. A circle of nut and bolt assemblies 46 pass through suitable registering openings formed in flange 36, spacer 40, and a top end plate 48 of the sample section 30 to thereby hold the three members 36, 40 and 48 together.

Within tubular member 34 are located, starting from spacer 40, a colliminator block 50 which serves to confine the beam of X-rays, and a source assembly 52, Assembly 52 comprises a mounting block 54 formed with a central opening in registry with the opening in colliminator 50, and with a recess at its rear end in which is positioned a foil of rhodium 56 mounted on a spacer block 58, which block 58 in turn is mounted at its rear end or outer face to a mounting plate 60. The plate 60 is held onto block 54 by suitable screw and washer assemblies 62. The foil 56, spacer block 58, and mounting plate 60 are secured together as mounting plate 60 is tightened down by the screws of assemblies 62. In spaced relation to the active face of the rhodium foil block 54 is formed with a 45 passageway 64. A rear enlarged portion of passageway 64 contains the radioactive americium 241 source 66, which is held in place by a threaded locking plug 68. Thus, a reflection mode source is provided.

Means are provided to seal the source and to permit adjusting the position of the entire source assembly 52 with respect to sample section 30. To this end, an end cap 70 is mounted on threads 38. Cap 70 is formed with a central threaded opening 72 which receives an adjusting rod 74 having its inner end secured, by welding or the like means, to the inner face of mounting plate 60. A lock nut 76 is mounted on threaded rod 74 to fix the adjusted position of the rod, and hence of the source assembly 52, with respect to the cap 70. To prevent unauthorized access to the source and as a safety feature, end cap 70 and tubular member 34 are provided with a hasp and lock assembly 78.

To assemble the source for use, the rhodium and americium 241 active elements are mounted into block 54 using the usual safety precautions when handling radioactive materials. Plate 60 is mounted on block 54 by means of the screws 62. Then, with the use of suitable remote or long handled devices, not shown, on the end of rod 74, the assembly 52 with the assembled source, and with the end cap 70 on the rod 74, is inserted in the main housing or tubular member 34. The end cap 70 is then secured on the threads 38, the source assembly moved down to the position determined by the length of colliminator 50, the lock nut 76 fixed in position, and the hasp and lock assembly 78 secured. As is clear, the source can be moved further from the sample as needed by simple loosening of lock nut 76. The adjustment provided by rod 74 is needed to adjust the counting rate obtained. It is desired that the counting rate be as high as the electronics can handle accurately, so as to have the best statistical correctness.

The sample section 30 is shown in greater detail in FIGS. 3, 4 and 5. A bottom end plate 80, similar to top end plate 48, is provided, and the two plates 48 and 80 together define the length of the sample section 30. The plates are held together by means of four support members 82. The plates 48 and 80 and members 82 may be assembled together by means of screws, welding, or the like. A curved sample cell abutment wall 84 is provided within the support members 82 and surrounds slightly more than half the registering openings 86 formed in the two plates 48 and 80. The wall 84 is secured in position by means of its snug seat within a pair of suitably formed arcuate slots cut into the two end plates 48 and 80. The wall 84 is held within its slots by the action of the structural members 82 securing the plates together. Intermediate its ends, on its inside surface, wall 84 is formed with a sample cell holder ledge portion 88. At each of its outer ends, ledge 88 carries a sample cell positioning pin 90. Pin 90 may be secured in the ledge 88 by means of a press fit, mating threads, or the like. The centerlines of the pins 90 are located on a diameter of registering openings 86 and the overall extent of ledge 88 and is more than 180 so that the sample cell 92 will seat securely on the ledge.

Means are provided to enclose the sample cell 92 when it is in operative position in the sample section 30. To this end, a door 94 is hinged as at 96 to one end of back wall 84. Referring to FIG. 4, hinge means 96 comprises a fixed hinge half 98, a moveable hinge half 100, a hinge pin 102, and a torsion spring 104 coiled about pin 102 and disposed so as to urge door 94 normally closed. An elongated operating handle 106 is secured as by welding to door 94 adjacent the end thereof opposite hinge means 96. The handle 106 is sufficiently long to extend out beyond the plates 48 and so as to facilitate a users access to the sample cell 92.

Referring now to FIG. 4, the sample cell 92 of the invention is shown in detail. This device provides the ability to easily analyze various different materials and to permit safe handling so as to not create safety hazards. This cell also prevents decomposition of the sample due to loss of the volatile components thereof. In practice, a number of identical sample cells will be used with one analyzer.

Cell 92 comprises a body 108 of generally cylindrical shape, having a bottom end flange 110, an upper end flange 112, and an intermediate flange 114. Intermediate flange 114 is formed with a pair of locator openings 116 adapted to snugly but slidingly receive the pins to thereby accurately and reproducibly locate the cell 92 in the sample section 30. In this manner, and since the ledge 88 extends for more than 180, the operator is assured that the cell 92 will always seat level and in the same relative position to the rest of the apparatus.

The lower end of body 108 is formed with a composite opening to receive, in order of assembly of the parts, an O-ring l 18, a window 120, and a closure ring 122. A plurality of screws 124 pass through suitable openings in ring 122 and mate with threaded openings in bottom flange 110. The window 120 is preferably made of beryllium or other material which is transparent to X-rays, as is well known.

At its upper end the cell 92 comprises means to permit placing different samples in body 108, while at the same time providing means to permit the X-rays to pass through the sample cell. To this end, the upper end of the body is formed with a composite opening, similar to the structure at the lower end, to receive a second O-ring 1 18 and a second window 120. Additionally, for the purpose of providing added strength, a frame disc 126 is provided to enclose the edge portion of the upper window 120, and to cooperate with a top flange 128 of the end cap 130 of the cell 92. The cap 130 is secured to flange 112 by means of mating threads 132. The various parts are so dimensioned that the outside diameter of cap 130 will be substantially equal to the outside diameter of bottom flange so that the cell will fit snugly into the analyzer section. With the exception of the windows and O-rings 118, the sample cell 92 is preferably made of aluminum for light weight and for corrosion resistance to the various hydrocarbon fluids which are handled. The outside cylindrical surface of cap is preferably knurled to facilitate manipulating the cap on to and off of the threads 132. Tongs, not shown, are provided for moving the cell into and out of the sample chamber.

Referring back to FIG. 1, the pulse generating section 32 comprises a body 134, having a flange 136 at its inner end. A plurality of nut and bolt assemblies 138 secured the flange 136 to bottom end plate 80 of sample section 30, and also to a table, stand, or other fixed support 140. Within body 134 is positioned a colliminator 142, which is similar in structure and function to the colliminator 50 described above. After colliminator 142, there is provided a scintillation crystal 144, followed by a photomultiplier tube 146 and a preamplifier 148. The three items 144, 146 and 148 are purchased, and the user will provide those components which he desires to be compatible with whatever electronics 18 and 24 are utilized, as described above. A composite spacer 150 locates the three elements 144,

146 and 148 in the body 134. A base spacer 152 is provided at the end of spacer 150 and cooperates with a cap 154 threadedly mounted on the end of body 134. The lines 14 and 16 extend through a suitable opening in cap 154, and suitable sealing means, not shown, are provided around these leads.

The use of the radioactive source combination of the invention to produce a narrow band of energy at about 20 Kev is critical because the mass attenuation coefficients of carbon and hydrogen are virtually identical at 20 Kev. The basic glationis as to llows:

wherein I is the amount of X-rays transmitted through the sample cell, I is the amount of X-rays incident on the sample, e is the natural log base, it is the sample thickness presented to the X-rays, u a and u s are the mass attenuation coefficients for hydrogen, carbon, and sulfur respectively, W W and W are the Weight fractions of hydrogen, carbon, and sulfur in the sample, respectively, and p is the density of the sample. The density and thickness terms are made into a known quantity by simply always providing the same weight of material. Since weight equals density times volume, changes in density of sample material will be automatically corrected for by inverse changes in volume so long as weight is held constant. t is directly proportional to volume since the cell has a constant crosssectional shape. The volume of cell 92 is large enough to accommodate the largest volume that would reasonably be encountered. In this equation, I and l, are measured quantities, and t and p are known quantities. The assumption is made that there is nothing in the process stream other than carbon, hydrogen, and sulfur, which assumption produces correct results since only traces of other materials are present, and they may be ignored. The sulfur content of typical refinery hydrocarbon materials with which the invention has been used have been on the order from about 0.02 to about 5 percent, although there is theoretically no upper limit on the amount of the sulfur or other third element that can be detected by the invention. In any case, since in use, u is equal to u Equation 1 above can be rewritten and slightly rearranged as follows:

s P( n( u c)+ s s) (2) Since the sample has appreciable quantities of only carbon, hydrogen, and sulfur, the following equation is valid:

W +W +W l rearranging:

s u c) Substituting Equation (4) into and rearranging only the right hand side of Equation (2) P( n( s) s s) pulu s n s s) P0 s( u .9))

Since the t and p, u and u all have known values, it is valid to substitute the following constants K and K Substituting Equations (8) and (9) into Equation (7), Equation (2) appears as follows:

e o i z s) Thus, the amount of transmitted X-rays is directly proportional to only the weight percent of sulfur in the sample. It will be understood by those skilled in the art that Equation (10) above can be normalized to some standard material having properties closely related to those materials with which the invention will be used.

The term appreciable quantities of only as used in the specification and claims herein means that any minute or trace quantities of any other additional substance which might also be present is not large enough to adversely effect operation of the invention. As is known, such spurious substances are sometimes present in hydrocarbon streams in insignificant amounts.

The invention is highly sensitive to changes in the weight fraction of sulfur, and relatively insensitive to changes in the weight fractions of hydrogen and/or carbon. As stated above, a is almost identical to u at about 20 Kev. Additionally, specifically for the element sulfur rather than any third element, the value of u at b u .2 K visqn th .Qr. ..9.=1b t 8iim@ a great as the value of u or u at about 20 Kev. TherefcTreIa change of, for example 1 percent in either W or W as by the addition of a sulfur free hydrocarbon to the process stream, will have a much less than 1 percent change on W Therefore, the apparatus of the invention is highly sensitive to change in W in the process stream.

As the above line of reasoning clearly shows, the invention is adaptable to analyze for any element so long as its mass attenuation coefficient is substantially different from that of hydrogen and carbon at about 20 Kev.

As stated above, the method of the invention utilizes the fact that the mass attenuation coefficients of hydrogen and carbon are almost identical at about 20 Kev, which is the energy level produced by the source of the invention. If another source which produces an energy peak and average value close to 20 Kev were used, the accuracy of such a device would depend upon how close to 20 Kev the energy was. If it were very close, for example, 20.5 Kev, the accuracy would still be acceptable for all uses. The invention encompasses all such sources that produce an energy level so close to 20 Kev that the resulting accuracy will be sufficient for the purposes for which the hydrocarbon is being analyzed. The range of energy which will produce acceptably accurate results for most purposes is thought to be 20 Kev plus of minus one Kev. Even larger ranges can be used if corresponding lower accuracy can be tolerated.

The energy peak obtained with the source of the invention is an important factor in the exceedingly high accuracy of the invention in determining percent third element content. As explained above, the invention depends upon the fact that the mass attenuation coefficients for hydrogen and carbon (a and 14 are equal at about 20 Kev. If the source does not produce a sharp peak at about 20 Kev then u will only be approximately equal to a dependent upon how close the average energy of the spectrum is.

Referring to the curves of FIGS. 6 to 8, the advantageous energy spectrum obtained with the americiumlrhodium source of the invention as compared to the energy spectrum of other sources, and other test results,

are shown. The curves of FIG. 6 show these comparative results, and the drawing is relatively selfexplanatory. The Y axis is an arbitrary measure of activity and the X axis is proportional to energy produced by the three different source combinations shown. Referring to FIG. 7, the curve C shows how the mass attenuation coefficient for carbon varies at different X-ray energies. The curve H shows how the mass attenuation coefficient for hydrogen is substantially constant over the energies tested. The significant point is that the curves C and H cross at almost exactly 20.25 Kev. Thus the term about 20 Kev" as used in the specification and claims hereof shall be understood to mean, in accordance with these empirical results, substantially 20.25 Kev. Now referring back to FIG. 6, it can be seen that the curve for the Am/Rh source combination of 3 energy, i.e., closest to its peak, for the particular target 7 material. The curves of FIG. 8 illustrate how the error in sulfur content varies with changing carbon hydrogen ratio. For silver, the error is in the positive direction for low carbon hydrogen ratios, and changes to the negative direction for the heavier materials. For the molybdenum/americium source combination the opposite is true. For the rhodium/americium source arrangement of the invention the error response is virtually flat. Thus, the invention substantially eliminates the effect of the carbon hydrogen ratio as a factor in inducing error in the finally determined percent sulfur content. In the prior art, the adverse effect of different carbon/- hydrogen ratios on accuracy was not corrected. In the embodiment of the invention which has been built and successfully used, the following purchased components were used:

TABLE Part No. DESCRIPTION Manufacturer Model No. 12 Power supply Canberra 3002 8c 1400 18 Amplifier Canberra 1415 10 20 SCA Canberra 1431 24 Timer Canberra 149i 26 Sealer & Output Canberra l49l 144 Crystal Harshzw SSHBl 146 Photomultiplier Harshaw SSI-IB] 148 Pre-amplifier Canberra 1405 The sample cell 92 had a volume of 35 cc. Temperature does not have an effect on results because a constant mass is weighed into the cell and this potential source of error is accommodated by simply allowing the sample cells with the samples therein to equalize to room temperature prior to analysis. The rhodium foil 56 used had a diameter of about one and one-half inches and a thickness of about 0.016 of an inch. It is thought that foil thicknesses ranging from 0.005 inch and greater could also be used. An Americium source of 300 mc was used.

While the invention has been described in detail above, it is to be understood that this detailed description is by way of example only, and the protection granted is to be limited only within the spirit of the invention and the scope of the following claims.

We claim:

1. A method of determining the percent content of an element in a hydrocarbon material containing appreciable quantities of only hydrogen, carbon and said element, comprising the steps of producing a stationary sample of said hydrocarbon material of known weight, producing fluorescent X-rays from an Americium- 241 /Rhodium reflection mode radioactive source, passing said X-rays through said stationary sample, and generating a signal proportional to the percent content of said element in said stationary sample based upon the amount of X-rays transmitted through said stationary sample.

2. Apparatus for determining the amount of an element in a hydrocarbon material containing appreciable quantities of only hydrogen, carbon, and said element, means for containing a sample of said hydrocarbon material of known weight, source means for producing fluorescent X-rays having a relatively sharp energy peak at about 20.25 Kev, means to subject said sample to said X-rays, means to measure the amount of X-rays passed through said sample, whereby the percent content of said element in said sample may be determined based upon said amount of X-rays transmitted, and said source means comprising radioactive Americium-241 and a Rhodium target arranged in reflection mode.

3. The combination of claim 2, said sample containing means comprising a removable sample cell, said apparatus comprising a sample section, means for removably and reproducibly positioning said sample cell in said sample section, said means to subject a sample in said sample cell to said X-rays comprising window means at the opposite ends of saidsample cell along the path of passage of said X-rays through said sample cell, and cap means at one end of said sample cell associated with one of said window means to facilitate changing the sample in said sample cell.

4. The combination of claim 3, said sample cell being of generally cylindrical configuration, said locating means comprising a ledge portion in said sample section intermediate the ends thereof, said sample cell comprising a flange portion for seating upon said ledge portion, and mating pin and opening means between said ledge portion and said flange portion.

5. The combination of claim 4, said ledge portion of said sample section extending for more than 180 about the centerline of a sample cell seated thereon.

6. The combination of claim 5, and door means on said sample section spring loaded to the closed position against said ledge portion, whereby a sample cell in said sample section is completely enclosed during analysis.

7. The combination of claim 4, said pin and opening means comprising a pair of pins fixed to said ledge portion in spaced relation to the ends thereof, and a plurality of openings for snugly and slidingly receiving said pins formed in said flange portion.

8. The combination of claim 3, said window means comprising two beryllium discs removeably mounted one at each end of said removeable sample cell.

9. The combination of claim 2, said apparatus comprising a sample section and a source section, and means to control the X-rays from said source section impinging upon said sample section.

10. The combination of claim 9, said X-ray control means comprising a spacer member interposed between said sample section and said source section, and said spacer member being formed with a slot for removeably receiving an X-ray blocking strip to thereby block a varying part of the X-rays passing between said sections.

11. The combination of claim 2, said X-ray measuring means comprising a series array of a crystal scintillation counter, analyzing means, means for discriminating against all energies transmitted by said amplifying means other than those energies at about 20 Kev, and output means for displaying the output of said discriminator means in a manner proportional to the percent content of said third element in said hydrocarbon sample.

12. The combination of claim 4, said sample section comprising a cylindrical abutment wall for receiving said sample cell, said sample cell comprising lower end flange means of a diameter substantially equal to the diameter of said upper end cap means for contacting said abutment wall.

13. The method of claim 1, wherein said element is sulphur.

14. The method of claim 1, wherein said element is lead. 

2. Apparatus for determining the amount of an element in a hydrocarbon material containing appreciable quantities of only hydrogen, carbon, and said element, means for containing a sample of said hydrocarbon material of known weight, source means for producing fluorescent X-rays having a relatively sharp energy peak at about 20.25 Kev, means to subject said sample to said X-rays, means to measure the amount of X-rays passed through said sample, whereby the percent content of said element in said sample may be determined based upon said amount of X-rays transmitted, and said source means comprising radioactive Americium-241 and a Rhodium target arranged in reflection mode.
 3. The combination of claim 2, said sample containing means comprising a removable sample cell, said apparatus comprising a sample section, means for removably and reproducibly positioning said sample cell in said sample section, said means to subject a sample in said sample cell to said X-rays comprising window means at the opposite ends of said sample cell along the path of passage of said X-rays through said sample cell, and cap means at one end of said sample cell associated with one of said window means to facilitate changing the sample in said sample cell.
 4. The combination of claim 3, said sample cell being of generally cylindrical configuration, said locating means comprising a ledge portion in said sample section intermediate the ends thereof, said sample cell comprising a flange portion for seating upon said ledge portion, and mating pin and opening means between said ledge portion and said flange portion.
 5. The combination of claim 4, said ledge portion of said sample section extending for more than 180* about the centerline of a sample cell seated thereon.
 6. The combination of claim 5, and door means on said sample section spring loaded to the closed position against said ledge portion, whereby a sample cell in said sample section is completely enclosed during analysis.
 7. The combination of claim 4, said pin and opening means comprising a pair of pins fixed to said ledge portion in spaced relation to the ends thereof, and a plurality of openings fOr snugly and slidingly receiving said pins formed in said flange portion.
 8. The combination of claim 3, said window means comprising two beryllium discs removeably mounted one at each end of said removeable sample cell.
 9. The combination of claim 2, said apparatus comprising a sample section and a source section, and means to control the X-rays from said source section impinging upon said sample section.
 10. The combination of claim 9, said X-ray control means comprising a spacer member interposed between said sample section and said source section, and said spacer member being formed with a slot for removeably receiving an X-ray blocking strip to thereby block a varying part of the X-rays passing between said sections.
 11. The combination of claim 2, said X-ray measuring means comprising a series array of a crystal scintillation counter, analyzing means, means for discriminating against all energies transmitted by said amplifying means other than those energies at about 20 Kev, and output means for displaying the output of said discriminator means in a manner proportional to the percent content of said third element in said hydrocarbon sample.
 12. The combination of claim 4, said sample section comprising a cylindrical abutment wall for receiving said sample cell, said sample cell comprising lower end flange means of a diameter substantially equal to the diameter of said upper end cap means for contacting said abutment wall.
 13. The method of claim 1, wherein said element is sulphur.
 14. The method of claim 1, wherein said element is lead. 